ROS2 Diff drive control demo

#ros2   #control2   #demo   #diff-drive   #ignition  

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Table of Content

ROS2 Diff drive control demo

github

sudo apt install ros-humble-ign-ros2-control-demos

ros2 launch ign_ros2_control_demos diff_drive_example.launch.py

Demo: Move robot using teleop

ros2 topic list
#
/clock
/diff_drive_base_controller/cmd_vel_unstamped
/diff_drive_base_controller/odom

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Run teleop cli

run teleop

ros2 run teleop_twist_keyboard teleop_twist_keyboard \
--ros-args --remap cmd_vel:=diff_drive_base_controller/cmd_vel_unstamped

Run teleop from launch file

launch teleop

import launch
from launch_ros.actions import Node


def generate_launch_description():
    ld = launch.LaunchDescription()
    teleop = Node(
        package="teleop_twist_keyboard",
        executable="teleop_twist_keyboard",
        output='screen',
        name="teleop_demo",
        prefix = 'xterm -e',
        remappings=[
            ('/cmd_vel', '/diff_drive_base_controller/cmd_vel_unstamped'),
        ]
    )


    ld.add_action(teleop)
    return ld

xterm -e

Running node that need stdin in separate terminal using

Node argument

prefix = 'xterm -e',

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tf tree

ros2 run rqt_tf_tree rqt_tf_tree

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Controllers

• joint_state_broadcaster
• diff_drive_base_controller

load controllers using ExecuteProcess

Launch

check launch file

• Using event to trigger action

ignition_spawn_entity → load_joint_state_controller → load_joint_trajectory_controller

from launch.actions import ExecuteProcess

load_joint_trajectory_controller = ExecuteProcess(
    cmd=['ros2', 'control', 'load_controller', '--set-state', 'active',
            'diff_drive_base_controller'],
    output='screen'
)

from launch.actions import RegisterEventHandler
from launch.event_handlers import OnProcessExit

RegisterEventHandler(
    event_handler=OnProcessExit(
        target_action=load_joint_state_controller,
        on_exit=[load_joint_trajectory_controller],
    )
),